紫外光交联聚乙烯的结晶行为

Crystallization Behavior of UV-photocrosslinked High-density Polyethylene

采用熔融共混法制备了高密度聚乙烯(HDPE)/光引发剂(BDK)/交联剂(TAIC)共混物,在高压汞灯辐照下制备了一系列不同交联程度的样品。通过广角X射线衍射(XRD)与差示扫描量热法(DSC)等测试技术研究了紫外光交联对HDPE的晶体结构及非等温结晶动力学行为的影响。结果表明,紫外光交联不改变HDPE晶型。随着光交联时间的增加,结晶峰的强度下降,晶粒尺寸变小。随着降温速率的增加,HDPE与交联HDPE(XLPE)的结晶峰变宽,结晶温度(Tp)向低温方向移动,结晶速率变快,结晶度(Xc)下降。相比较而言,XLPE的Tp较低,F(T)较大,Xc较小,结晶活化能(ΔE)较高,表明紫外光交联抑制了HDPE的结晶。

High-density polyethylene （ HDPE ）, a photoinitiator （ benzil dimethyl ketal, BDK）, and a crosslinker（ triallyl isocyanurate, TAIC ） were mixed at elevated temperature, and then a series of samples with different degrees of crosslinking were prepared by UV photocrosslinking under a high pressure mercury lamp. The effects of ultraviolet （ UV ） photocrosslinking on the crystal structure and non-isothermal crystallization kinetics were studied by means of X-ray diffraction （XRD） and differential scanning calorimetry （DSC）. The results show that UV phtocrosslinking did not change the crystal type of the HDPE. However, the degree of erystallinity and the size of the crystals decreased with increasing UV irradiation time. With the cooling rate increasing, the crystalline peaks of both neat HDPE and photocrosslinked HDPE （XLPE） became wider, and the crystallization temperatures（ Tp ） moved toward lower temperature, the crystallization rate increased, and the degrees of crystallinity （Xc ） were reduced. In comparison with un-photocrosslinked HDPE, XLPE possesses lower Tp, bigger F（ T）, smaller Xc and higher effective activation energy（ △E）, indicating that UV photocrosslinking suppresses the crystallization process of HDPE.